Many local area networks (“LANs”) are connected to the Internet or another wide area network (“WAN”). LANs may also be connected to one another through the Internet or another WAN. A given LAN, or a given sub-network of a LAN, is connected to the WAN through a device known as a router. For convenience, reference is made hereafter to LANs with the understanding that “LAN” means “LAN or sub-network” unless otherwise stated. Routers use both WAN addresses, such as Internet Protocol (“IP”) addresses, and physical addresses, such as Ethernet addresses. Physical addresses may also be called “data link addresses”.
Each router receives from its LAN all network traffic addressed to a destination outside the LAN, such as data packets addressed to a remote IP address. The router forwards those packets to the next router along a path to the destination. The path often takes the packet through part of the Internet or another WAN. The router likewise receives Internet or other WAN packets from other LANs which are destined for machines within the router's LAN, and re-directs the packets so they can be delivered using physical addresses which are internal to the LAN. Conversion from an IP address to a data link address such as an Ethernet address may be done using a conventional Address Resolution Protocol (“ARP”). Some known systems use two or more routers with a form of inflexible load balancing, whereby all requests go out over a first router and all responses come back over a second router.
FIG. 1 illustrates a conventional network topology 100 which uses a router to connect a LAN (or sub-network, as noted above) to a WAN. Several nodes 102 are connected by LAN “wires” in a LAN 106. The nodes 102 may include machines such as desktop computers, laptops, workstations, disconnectable mobile computers, mainframes, information appliances, personal digital assistants, and other handheld and/or embedded processing systems. The “wires” 104 may include twisted pair, coaxial, or optical fiber cables, telephone lines, satellites, microwave relays, modulated AC power lines, and/or other data transmission “wires” known to those of skill in the art. The network 106 may include UNIX, TCP/IP based servers; Novell Netware®, VINES, Microsoft Windows NT or Windows 2000, LAN Manager, or LANtastic network operating system software (NETWARE is a registered trademark of Novell, Inc.; VINES is a trademark of Banyan Systems; WINDOWS NT, WINDOWS 2000, and LAN MANAGER are trademarks of Microsoft Corporation; LANTASTIC is a trademark of Artisoft).
Another “wire” 108 connects a router 110 to the LAN 106. A wide variety of routers 10 are known in the art. At a minimum, the router 110 maintains a table of routes for different destination addresses. Different routers 110 can handle different physical address types (Ethernet, . . . ). Some routers provide firewall services. Different routers also handle connections that run at different speeds using different line technologies (T1, T3, ADSL, RADSL, . . . ). But in general, some type of high-speed connection 112 connects the router 110 to a WAN 114.
The Internet or a portion of the Internet may serve as the WAN 1114, or the WAN 114 may be separate from the Internet. “Internet” as used herein includes variations such as a private Internet, a secure Internet, a value-added network, a virtual private network, or a wide area intranet. Another connection 116 connects a server 118 or other destination with the WAN 114.
Like the illustrated topology 100, other conventional network topologies utilize one router per LAN (or sub-network). Conventional network topologies do not support the routing of data over multiple routers in any given LAN. For instance, standard TCP/IP stacks are not able to direct data packets from a given LAN to multiple routers when the data needs to be sent to another LAN. Multiple routers may be physically present, but one router is designated as the default gateway for the LAN. This default gateway receives all the traffic for the LAN from outside, and forwards data packets from inside the LAN to the next LAN on their way to their destinations.
The router 110 which serves as the default gateway also maintains a table of routes for different destination addresses. Data transmission generally takes place between two networks over the shortest defined path, where a path is represented as a list of routers which the data has to traverse in order to reach the destination node. For instance, a data packet from a given node 102 addressed with the IP address of the server 118 will be sent from the node 102 over the LAN wires 104, 108 to the gateway router 110, will travel from there over the high-speed connection 112 to the WAN 114 (which may forward the packet along a path containing multiple routers), and will finally arrive at the server 118.
Once a node such as a client PC 102 on the LAN 106 performs the Address Resolution Protocol, the information is stored in an ARP table on the client PC 102. After this the PC 102 does not send an ARP request until a timeout condition occurs. ARP tables and ARP timeouts are used in conventional systems and they may also be used according to the invention. After an ARP request is sent because of a timeout, or for another reason (e.g., when an ARP table entry is made manually), IP communication starts with a SYN packet. SYN packets in and of themselves are known in the art.
Similar steps occur when a packet from the same node 102 is addressed to another node on a distant LAN. In place of the server 118 the path would include another router connected to the distant LAN. In its capacity as gateway for the distant LAN, the distant router would receive the packet from the WAN 114 and deliver it to the distant node.
For clarity of illustration, Internet Service Providers (“ISPs”) have not been shown in FIG. 1. However, those of skill in the art understand that one or more ISPs will often be located along the path followed by a packet which travels to or from a LAN node 102 over the Internet 114.
The configuration 100 is widely used but nevertheless has significant limitations. Although the data transmission speed over lines such as the line 112 is relatively high when compared to traditional analog telephone data lines, the available bandwidth may not always be sufficient. For instance, the number of users within the LAN 106 may increase to a point at which the data transmission capacity of the WAN connection 112 reaches its maximum limit. In order to obtain more bandwidth, a company could lease more expensive dedicated data lines 112 which have greater data transmission speeds, such as lines employing T3 or OC3 technologies.
To delay expensive upgrades to line technology and to the corresponding router technology, bandwidth can be used more efficiently. This might be done by compressing data, by combining different types of data to reduce the total number of packets, and by reducing unnecessary access to the WAN 114 through appropriate personnel policies. Tools and techniques for improving router 10 performance are also being developed and made commercially available. In addition, new data transmission technologies like ADSL, RADSL, and others are being proposed and developed. Although these technologies do not have as high a data transmission rate as T3 or OC3, they are several times faster than analog lines.
Moreover, U.S. Pat. No. 6,253,247 describes a mux device for assisting the transmission of a user's data between two computer networks. The mux device could be added to a system like that shown in FIG. 1 to increase the bandwidth of the connection 112 by using multiple modem connections. The mux device allocates exclusively to a user for a period of time at least two connections between the two computer networks. Each of the connections uses a telephone connection which is physically separate from the other connection(s) for at least a portion of that connection. The mux device also contains other components, and the application also describes and claims methods and systems.
U.S. Pat. No. 6,295,276 describes an invention which is related to the present invention. The invention of the '278 patent involves ARP (address resolution protocol) tools and techniques, while the present invention involves SYN (synchronization) tools and techniques.
However, taking the conventional measures noted above may still provide only a short-term solution. Despite such measures, demands on the line 112 can still quickly grow to exceed the bandwidth of the line 112, thereby forcing the LAN 106 owner to seriously consider an expensive upgrade in line 112 and router 110 technology, such as an upgrade from a T1 connection 112 to a T3 connection 112.
Accordingly, it would be an advancement in the art to provide another alternative for increasing the bandwidth available to connect a LAN with a WAN, without requiring a routing system upgrade to a substantially more expensive line technology. This can also enhance the reliability of the network by adding a redundant connection for network communication outage avoidance.
It would also be an advancement to provide such an alternative which is compatible with a wide variety of existing line technologies and routers.
Such improvements to LAN-WAN connectivity are disclosed and claimed herein.